Benzene is an aromatic organic compound. It was discovered in 1825, by the English physicist and chemist Michael Faraday. Its molecular formula is C6H6. Benzene is a colorless, clear, and highly flammable liquid with a pronounced characteristic odor. It has a density of 0.8787 g/mL, a boiling point of 176.2°F (80.1°C), and a freezing point of 41.9°F (5.5°C).
Benzene is only slightly soluble in water, but is completely miscible with chloroform, carbon disulfide, alcohol, carbon tetrachloride, ether, as well as other organic solvents. You should not confuse benzene with benzine, because the second one is not a pure chemical compound, but rather a mixture of petroleum hydrocarbons that is used as a solvent and a fuel.
Historical uses of benzene
The earliest uses of benzene date back in the last 19th and early 20th centuries. The odor of benzene was considered pleasant during this period, and for this reason it was used as an aftershave. However, in 1903, a German coffee merchant, Ludwig Roselius, made benzene popular by using it to decaffeinate coffee. Today, we know that benzene is a carcinogen, and, of course, using it on coffee and using it as an aftershave is definitely something that we do not do anymore. In addition, another popular early use of benzene was for degreasing metal.
But, since it was later known that it is toxic and carcinogenic, other chemicals which are less carcinogenic and toxic replaced benzene. In modern world, benzene is one of the top twenty widely used chemicals in the United States of America. Benzene is still used in a number of industrial processes in order to manufacture synthetic fibers, dyes, rubbers, lubricants as well as plastics. However, since benzene is toxic and carcinogenic, its non-industrial uses are very limited.
The main use of benzene is as an intermediate in order to make other chemicals, above all alkylbenzene, nitrobenzene, cyclohexane, cumene, and ethylbenzene. More than half of the entire benzene production is processed into ethylbenzene, which is a precursor to styrene. Styrene is used in order to make plastics and polymers, such as EPS and polystyrene. About 1/5 of the benzene production is used to manufacture cumene, which is required to produce acetone and phenol for adhesives and resins. About 10% of the world’s benzene production is consumed by cyclohexane.
It is mainly used in the manufacture of nylon fibers, which are processed into engineering and textiles plastics. Furthermore, smaller amounts of benzene are used in order to make certain types of drugs, pesticides, dyes, rubbers, explosives, detergents, and lubricants. Three years ago, the biggest consumer country of benzene was China, followed by the United States of America. Today, the production of benzene is expanded in Africa and the Middle East, whereas capacities in North America and Western Europe stagnate.
Toluene is usually used as a substitute for benzene, for example as a fuel additive. Even though the solvent-properties of the two are similar, toluene has a wider liquid range and is less toxic. Additionally, toluene is also processed into benzene.